1. Field of the Invention
The present invention relates to an improvement in a V-type engine.
2. Description of Related Art
Recently, there has been the growing tendency that V-type engines are loaded on many vehicle models because they have the characteristic that their engine is in a short full length. Furthermore, in order to reduce the weight of an engine, there is the tendency that at least a cylinder block is made from a light alloy containing aluminium or the like.
It is essential that a lubricating apparatus for the V-type engines does not impair a compact construction as a V-type engine. When oil passages are formed in the cylinder block made by die casting a light alloy with drills, a leakage of oil may cause a big problem so that they should be formed by withdrawing dies.
U.S. Pat. No. 4,494,494 and Japanese Utility Model Application Laid-Open No. 147,706/1985 disclose a lubricating apparatus for a V-type engine, in which a pair of right-hand and left-hand banks are disposed in a V-shaped form and a main oil gallery is disposed at a middle portion of the cylinder block at a position above a crank shaft between the banks. This presents the greater advantage from the structural point of view compared with the oil gallery disposed on a side portion of each of the banks. When the main oil gallery is disposed at the middle portion of the cylinder block, lubricating oil is supplied to a crank journaling portion through the main oil gallery. In this case, however, a plurality of the crank journaling portions should be disposed in a spaced relationship in an axial direction of the crank shaft so that a full length in which the plural crank journaling portions are formed ranges from one end portion to the other of the cylinder block, thus requiring the main oil gallery, too, to elongate over a full length in a lengthwise direction of the cylinder block.
In many cases, the cylinder block of the v-type engines contains a pump chamber. For example, a water-cooling type engine is provided with a water pump for supplying cooling water under pressures around the cylinder bores. For the V-type engine, it is preferred to form a pump chamber of the water pump at a middle portion between the right-hand and left-hand banks in order to allow an equal distribution of cooling water therebetween. It is also preferred to dispose the water pump at a position as low as possible to avoid exposure of an impeller to air at the time of reduction in water.
However, the disposition of a pump and related elements of the water pump at a low position presents the difficulty that the pump chamber to be disposed in the cylinder block interferes with the main oil gallery on one side of the cylinder block in an axial direction of the crank shaft. Accordingly, the pump has been heretofore disposed on one end portion in a center space of the V-shaped banks or offset toward the left-hand or right-hand side from the center portion in order to avoid an interference with the main oil gallery. The former case, however, suffers from the disadvantage that the impeller is caused to be exposed to air at the time when water is reduced, thus accelerating deterioration of the pump, or that the pump chamber cannot be formed in the cylinder block, thus making a full engine length longer. In the latter case, for example, the problem may arise such that it is difficult to equally distribute cooling water between the right-hand and right-hand banks.
Recently, a knock sensor for sensing a knocking of the engine is generally provided on the cylinder block of the engine. For V-type engines, a knock sensor is provided on the cylinder block. For example, Japanese Patent Application Laid-Open No. 101,839/1987 discloses a knock sensor which is mounted at a center portion of a rib disposed on the cylinder block at a substantially middle portion in an axial direction of the crank shaft so as to connect the right-hand bank to the light-hand bank. An additional disposition of the rib, however, presents the disadvantages in terms of cost and structure.